High fidelity sound system



Feb. 1, 1955 e. H. KUHL 2,701,025

HIGH FIDELITY SOUND SYSTEM Filed Feb. '5, 1952 IN VEN TOR.

George/ KM BY/W/ W} United States Patent HIGH FIDELITY SOUND SYSTEMGeorge H. Kuhl, Glen Ellyn, Ill.

Application February 5, 1952, Serial No. 27 0,085

3 Claims. (Cl. 181-30) This invention relates to a high fidelity soundreproducing system.

It is the general object of this invention to produce a new and improvedapparatus for the high fidelity reproduction of sound.

Recent years have seen noteworthy advances in electronic systems foraccurately and faithfully reproducing sound. Amplifying equipment, soundgenerators such as speakers, and other equipment, have been improved tothe extent where sounds can be reproduced with a faithfulness heretoforethought impossible. Similar advances have taken place in the art ofrecording sound for later reproduction. Long-playing records and wireand tape recordings are now being produced which can recreate, withaccuracy and fidelity, music and other sounds recorded therein.

One serious drawback to the faithful reproduction of sound stillremains. In ordinary sound reproducing systems the speaker or otherelement generating the sound is normally enclosed in a housing of somesort and all of the sound is generated from a very small area. This factcreates the illusion of music or other sound coming out of a box. Thiseffect is quite different from the effect on the listener of hearing alive orchestra symphony or other originator of sound in actualperformance. To take an extreme example, the average home listenertorecorded symphonies may purchase and install an excellent record player,a high quality pickup, preamplifier and amplifier and speakers capableof reproducing all of the notes which the human car can hear and yet,when listening to a record of a symphony orchestra, the feeling of depthwhich would be sensed at a live performance is lost. It is unrealisticto condense a symphony orchestra into a two cubic foot record playercabinet.

A number of attempts have been made to overcome this disadvantage, someof them extremely elaborate. For example, it has been proposed to maketwo recordings of, for example, a symphony orchestra with one recordinginstrument being located on the left side of the orchestra and the otherinstrument on the right side. When listening to the recordings both areplayed at once but one record is directed to the left ear of thelistener while the other, to the right ear. In such systems earphoneshave been used and the listener has one earphone connected to theinstrument playing one record and the other connected to the instrumentplaying the other record; or two speakers positioned on either side ofthe listener may be employed. Such systems, while helpful, arecumbersome, difiicult to synchronize and certainly undesirable forinstallation in a private home.

I have discovered, however, a compartively simple apparatus and methodof using the same which, when properly installed, gives the illusion ofdepth to a sound reproducing system. In the system of this invention thesounds are divided between low frequency sounds and high frequencysounds in a manner which is common in high fidelity speakers (such ascoaxial speakers or separate tweeters and woofers) which are usuallyemployed. Rather than placing both speakers in a single box, however,they are so arranged as to cause the high frequency sound to take adifferent, preferably longer, path from their origin to the listenerthan the sounds generated by the low frequency speaker. In the preferredform of the invention illustrated, the longer path is achieved bydirecting the low frequency generator directly toward a listening areato provide for the sounds generated thereby a relatively short pathwhile directing the sounds generated 2,701,025 Patented Feb. 1, 1955 bythe high frequency generator against a reflector for reflection towardthe listening area. This not only spreads the high frequency sound togive the illusion of sound coming from an area rather than a point, butalso causes the high frequency sound to travel a longer path. Thislonger path gives a feeling of depth to the sound. Apparently thefeeling of depth arises because of the fact that the same sound whichmay have a basic low frequency also has overtones in the higherfrequencies. Because of the differences in paths, the basic lowfrequency note reaches the ears of the listener slightly in advance ofthe high frequency overtones and this very slight difference in thearrival times of sounds to the ear of the listener creates an illusionof depth.

A high fidelity sound reproducing system installed and operated in themanner hereinafter to be described creates the illusion of a fullsymphony orchestra, for example, playing behind an imaginary opaquedrop, that is, as if it were playing just outside the room, and the fullexpanse and breadth of the orchestra can clearly be felt by thelistener.

The apparatus and its use will be described in connection with theaccompanying drawings, in which:

Fig. l is a front elevation of apparatus embodying the invention;

Fig. 2 is a vertical sectional view of the apparatus shown in Fig. 1;and

Fig. 3 is a horizontal sectional view taken near the upper portion ofFig. 1.

While this invention is susceptible of embodiments in many differentforms, there is shown in the drawings and will herein be described indetail one specific embodiment, with the understanding that the presentdisclosure is to be considered as an exemplification of the principlesof the invention and is not intended to limit the invention to theembodiment illustrated. The scope of the invention will be pointed outin the appended claims.

While it will be clear to those skilled in the art that the soundreproducing system of this invention can be utilized with many soundgenerating instruments such as electric organs and the like and that theprinciples of the invention can be utilized in installations of widelyvarying nature, for the purpose of brevity the invention will bedescribed for use in reproducing recorded sounds from a record and isshown as installed in a room.

Referring now to the drawings, it will be noted that the apparatus isinstalled in the corner 10 of a room having walls 11 and 12, meeting inthe corner at an angle of approximately and a ceiling 13 and floor 14.Extending diagonally across the corner from ceiling to floor is aclosure member 15 which may take the form of a plywood panel or othersuitable material usable in sound reproducing systems. The closuremember 15 together with the ceiling, walls and floor forms a chamber 16isolated except for a circular opening 17 therein. For the purposes ofenhancing the appearance, a suitable cloth grillwork such as thegrillwork 18, which may be rectangular or any other shape, covers theopening 17.

Mounted on the interior side of the closure member 15 is a low frequencysound generator in the form of a speaker 20. The chamber 16 in which thelow frequency speaker is located provides a rather large isolated volumeof air. Corner space in a room is often unusable for any purpose andthus by utilizing a corner, a great deal more of isolated air space forthe speaker can be obtained without detracting from the appearance ofthe room. The closure member 15 may be finished to resemble the otherwalls of the room so as to be comparatively inconspicuous. A furtheradvantage of corner location is that the diverging walls act asextensions of the horn of the speaker and improve its performance.

High frequency speakers 21 and 22 (which are known as tweeters in theart) are located exteriorly of the chamber 16 and are directed away fromthe listening area, the direction of said area being in the directionfaced by the low frequency speaker 20. Preferably the high frequencygenerators are mounted in a cabinet 23 which rests upon the floor 14 ofthe room. The cabinet may be provided with a suitable turntable 24,preamplifier 25 and amplifier 26 of the electronic sound reproducingequipment. The amplifier is connected to a suitable crossover network 30which functions to divide the electrical impulses received in accordancewith the frequency of the sound to be generated in a manner well knownin the art. Preferably the crossover network is so constructed as todeliver to the low frequency generator 20, through line 31, electricalimpulses for producing sound of 850 cycles and lower. While a singlehigh frequency generator may be employed, I prefer to employ two and toarrange the crossover network so as to deliver to the generator 21electrical impulses for reproducing sounds having from 850 to 2500cycles and to utilize the lead 33 to deliver to the high frequencygenerator 22 electrical impulses for reproducing sounds over 2500cycles. By the employment of a high frequency generator, such as thegenerator 21, and an extra high frequency generator, such as the speaker22, a further improvement in the illusion of reality can be achieved.

The high fidelity generators are directed upwardly and away from thelistening area against an angularly inclined reflector 40 locatedadjacent the ceiling. The reflector 40 is constructed of high fidelitysound reflecting material such as glass, steel, tile and the like andserves to reflect the high frequency sounds outwardly toward and intothe listening area. Because of the circuitous path followed by the highfrequency sounds, their path of movement to a listener in the listeningarea is longer than the path of movement of low frequency sounds fromthe low frequency driver 20.

The reflecting panel 40 is substantially trapezoidal in shape and cut tofit the corner in which it is installed. Thus, the shorter base 41 restsagainst the closure member 15 while the longer base 42 is locatedadjacent the ceiling of the room with the sides 43 and 44 being adjacentthe walls 11 and 12 respectively.

While improvement over ordinary installations can be accomplished bylocating the reflector within the chamber 16 and also moving the highfrequency speakers within the chamber, the results are inferior to thoseproduced with the arrangement shown in the drawings inasmuch as with thelatter arrangement, a far better dispersion of sound occurs whichenhances the illusion referred to of the sound originating from an arearather than from a point. If the walls 11 and 12 are of ordinaryplaster, they possess some sound absorbing qualities. If the plaster isextremely hard, however, or if walls which have a high reflectivity forsound are encountered, improved sound characteristics can be obtained byinsulating with sound deadening material the exterior surfaces of thewalls within the chamber.

I claim:

1. Apparatus for increasing the fidelity of a roominstalled soundreproducing system comprising a closure member extending from theceiling to the floor of the i member extending from adjacent the ceilingto the floor within the chamber and directed outwardly therefrom towarda listening area, an angularly inclined reflector positioned exteriorlyof the chamber adjacent the ceiling and a high frequency generatorpositioned exteriorly of the chamber and substantially verticallybeneath said reflector, said high frequency generator being directedupwardly toward the reflector.

2. Apparatus for increasing the fidelity of a roominstalled soundreproducing system comprising a closure of the room diagonally across acorner thereof to provide with the walls, ceiling and floor an isolatedchamber, a low frequency generator mounted on the closure member withinthe chamber and directed outwardly therefrom toward a listening area, anangularly inclined reflector positioned exteriorly of the chamberadjacent the ceiling, and a high frequency sound generator positionedexteriorly of the chamber substantially vertically beneath the reflectorand directed upwardly and away from the listening area toward thereflector.

3. Apparatus for increasing the fidelity of a roominstalled soundreproducing system comprising a closure member extending from adjacentthe ceiling to the floor of the room diagonally across a corner thereofto pro vide with the walls, ceiling and floor an isolated chamber, a lowfrequency generator mounted on the closure member within the chamber anddirected outwardly therefrom toward a listening area, an angularlyinclined substantially planar reflector inclining outwardly toward thelistening area and extending from the upper portion of the closuremember substantially completely to the ceiling and horizontally fromwall to wall in the corner, and a high frequency sound generatorpositioned exteriorly of the chamber substantially vertically beneaththe reflector and directed upwardly and away from the listening areatoward the reflector.

References Cited in the file of this patent UNITED STATES PATENTS2,143,175. Waite Jan. 10, 1939 2,217,279 Karns Oct. 8, 1940 2,275,610Bucky et a1 Mar. 10, 1942 2,310,243 Klipsch Feb. 9, 1943 2,539,327 Reidet a1. Ian. 23, 1951 2,610,694 De Boer Sept. 16, 1952 2,612,234Zivadinovic Sept. 30, 1952 FOREIGN PATENTS 929,705 France Jan. 6, 1948

